As underground pipe ages or otherwise becomes inadequate for its purpose, there is a need to replace it with new pipe. Preferably, pipe replacement is performed with minimal impact to the surrounding environment, be it the disruption of normal traffic or the ground area needed to operate the equipment. Further, it is preferable to minimize the time expended setting up and repositioning the equipment used to conduct the pipe replacement.
Apparatus and process exist which meet several of the above goals with varying degrees of success. Minimizing the disruption of traffic is accomplished with a method for replacing pipe without digging a trench along the entire length of pipe.
Prior art processes comprise:
digging two pits into the ground to expose the old pipe; PA1 fishing a cable through the old pipe; PA1 using an abutting member to brace the cable against one end of the old pipe; PA1 placing apparatus in the other pit and using shoring timbers to support the apparatus against the pit wall and absorb reaction forces; PA1 pulling on the cable end and abutting member to pull the pipe from the ground and extract it from the pit; and PA1 optionally, attaching new pipe to the old pipe so as simultaneously pull new pipe into the bore through the ground formed by the extracted old pipe. PA1 a reaction plate for pressing or bracing against the side of the first pit's wall adjacent the first end of the old pipe for absorbing reactive forces generated through pulling of the pipe; PA1 a pulley mounted to the reaction plate for receiving the pipe-pulling cable extending out of the pipe and turning it through a right angle to extend up and out of the first pit; PA1 a structure extending up from the reaction plate to a cable winch; and PA1 the winch being attached to a moveable vehicle for enabling inserting of the reaction plate and connecting structure into the first pit. PA1 a mobile excavator (such as a backhoe) having an articulated boom having a tool end; PA1 a heavy box-like frame which is positioned in a first of the two pits; PA1 the frame contains and supports an actuator, preferably one or more double-acting hydraulic cylinders, for axially pulling or pushing the length of old pipe through the ground; PA1 the frame and boom tool end each have elements of a quick-attach coupling, the elements being operative to engage to lock the tool end and frame together, so that the boom may emplace in or remove the frame out of the pit and so that the excavator may be rigidly connected to the frame to anchor it and prevent it from twisting when pulling pipe; PA1 preferably the coupling being operative to swivel although it can be pinned to prevent swivelling when appropriate; PA1 a reaction plate structure, preferably detachable, which is connected with the frame, for bearing against the pit wall during pulling; PA1 and a pulling member, preferably comprising a series of short segments (such as cables or rods) joined end to end by separable joints, the pulling member having means such as a plate abutting the end of the old pipe length at the second pit, said pulling member extending through the bore of the old pipe length into the first pit; PA1 the actuator being connected to the pulling member for pulling it and the old pipe length. PA1 by the addition of providing a bucket with a quick-attach element, a backhoe can be used to excavate the pits, to move the frame into and out of the first pit, to operate the actuator, and to anchor the frame, thereby accelerating the pipe removal operation relative to what was commonly practised in the past in this connection, using a minimal number of pieces of equipment to do the work; PA1 by providing an anchored frame, the time-consuming operation of shoring the pit with timbers has been eliminated; PA1 the frame provides a rigid immovable connection between the cylinder and the reaction plate, thereby ensuring that the assembly does not twist; PA1 by providing a separate, disengageable, movable reaction plate structure in conjunction with a hydraulic cylinder actuator, the assembly can be converted quickly between pipe pulling and pipe pushing modes. Having both modes available improves the versatility of the system. PA1 a tubular member; PA1 a connector at the leading end of the tubular member for attaching to the extraction cable extending from the old pipe; PA1 a connector at the trailing end of the pig and inset therein for attaching to an insertion cable extending through the new pipe; PA1 means for abutting the insertion cable's pulled-end against the new pipe's far end so that when the extraction cable is pulled, the pig is pulled, the old pipe is urged from the ground, the pig pulls the insertion cable and the new pipe is urged into the ground, the leading end of the new pipe being protected from debris as it is inset within the pig. PA1 providing an excavator having a movable boom and a tool end having quick-connection to two or more tools including an excavating bucket; PA1 installing the excavating bucket and digging first and second pits to expose a first and second ends of the old pipe; PA1 extending an extraction cable through the old pipe, having a pulling end and a pulled end, an abutment member securing the pulled end against the second end of the old pipe; PA1 substituting the excavating bucket with a pipe-pushing/pulling frame, the frame having a cable-pulling actuator and a reactive face plate; PA1 positioning the frame into the first pit with the cable-pulling actuator aligned with the old pipe and then arresting movement of the boom so as to substantially prevent movement of the tool end relative to the vehicle; PA1 connecting the cable-pulling actuator to the pulling end of the extraction cable extending from the first end of the old pipe; PA1 actuating the cable-pulling actuator to pull the extraction cable and induce the pulled end of the extraction cable and the abutment member to push on the second end of the old pipe and extract the old pipe from the ground while the pipe-pushing/pulling frame is supported against reaction forces firstly by the reaction face plate bearing against the pit wall and secondly by the arrested boom preventing twisting. PA1 providing an insertion cable extending through new pipe and a new-pipe abutment member, connected to the pulled-end of the insertion cable and abutting against the new pipe's trailing end PA1 substituting the old-pipe abutment member with a tubular pig having first and second ends the pig's second end receiving the leading end of the new pipe, an old-pipe abutment member at the pig's first end, a first extraction cable-connector located at the pig's first end, and a second insertion cable-connector located within the bore of the pig's second end; PA1 connecting the cable-pulling actuator to the pulling-end of the extraction cable extending from the first end of the old pipe, connecting the pulled-end of the extraction cable to the pig's first cable-connector and connecting the pulling-end of the insertion cable to the pig's second cable-connector; PA1 actuating the cable-pulling actuator to pull on the extraction cable to pull the pig through the ground to simultaneously extract the old pipe and insert new pipe, the leading end of the new pipe being protectively housed within the bore of the member's second end.
The above process has been accomplished with a variety of equipment which applies many or all of the above method steps. Apparatus including that in U.S. Pat. No. 5,328,297 ('297) to Handford and 5,211,509 to Roessler disclose various forms of cable-winches and pulley arrangements comprising:
The reaction plate of Roessler is a permanent non-rotatable structure attached to the vehicle. The rigid structure of Roessler holds the reaction plate stable but restricts the positioning of the vehicle to a position directly in-line with and opposing the pipe. Further, a separate piece of equipment must be provided to dig the pits.
Handford '297 provides an assembly which comprises a cable winch, a downward extending leg assembly, pulley and reaction plate. The assembly is releasably attached at ground surface to a front end loader for using its hydraulic power system. The reaction plate is rotatable relative to vehicle so that the vehicle may positioned anywhere around the pit. The leg assembly permits vertical adjustment to match the reaction plate's depth to the exposed pipe. The reaction plate of Handford is dependent however upon the pit wall being square to the normal force applied to pull the pipe. If the pit wall is not square, the reaction plate will rotate on the leg, mis-aligning the cable pulley from the pipe and adversely affecting the vertical. As with Roessler, a separate piece of equipment must be provided to dig the pits.
The prior art deals with non-square pit walls by using shoring. Personnel enter the pit and arrange a variety of timbers to square the reaction plate to the pit walls. Release of cable-pulling tension can dislodge or release the shoring, causing it to lose its stacked structure which then requires time-consuming repositioning by the personnel. Further, for safety reasons, use of personnel working in the pit should be minimized.
Neither Handford '297 nor Roessler teach nor suggest how a pulling apparatus may be constructed for permitting the equipment to be positioned closely adjacent and freely about the pit while also conveniently stabilizing the apparatus against the pit wall without involving personnel in a significant way or eliminating the troublesome shoring.
Another difficulty associated with old buried pipe is that in some instances it is necessary to initially free the pipe before it is possible to use a cable to pull the pipe from the ground. Accordingly, there is often a need to first loosen the pipe prior to pulling with the cable. One method of loosening a stuck pipe is to alternately push, then pull the pipe. This is not possible either with the prior art cable pulling apparatus described above as they do not incorporate a pushing reaction plate or means for generating a pushing force.
In another approach disclosed by Handford in U.S. Pat. No. 5,205,671 ('671), a hydraulic pushing device is provided which pushes old pipe out of the ground using a hydraulic ram. The rams can also pull the old pipe from the ground. A pulling pipe is extended through the old pipe and an abutment member is used to bear against the distal end of the old pipe. New pipe is bolted to the abutment member and is pulled into the ground as the old pipe is drawn or pushed out. Handford '671's device is fitted with reaction plates on both ends but is otherwise unsupported. Accordingly, the device is long and must be shored against the pit walls to prevent unwanted reactive movement.
There is a therefore demonstrated a need for apparatus capable of independent positioning about the pit and having sufficient structural strength to brace the pulling apparatus against the pit wall without reactive movement. Significant advantage in time and cost is achieved if the above can be achieved without shoring and by using a single prime-moving piece of equipment upon which the pulling apparatus can be quickly substituted with a pit-digging or pulling implement. It is advantageous if such an apparatus has the ability to break a stubborn pipe free from the ground.